Kohler CV16s bent starter armature shaft

[lee]

All of the sudden the starter started making a terrible sound like the teeth were stripped. Took the starter off and found the armature shaft bent. The bendix drive still worked and the teeth on the pinion gear and flywheel still look good. I looked over the flywheel to try to see what the pinion gear must have hit in order to bend the armature but I can't see anything obvious. The flywheel magnet is the only thing sticking out and that area looks fine. Question: What the heck did the pinion gear hit that bent the armature shaft? Is the problem with the flywheel or the starter motor? The starter motor is a WPS aftermarket unit that looks like it might be just a couple years old. Maybe the previous owner had the same problem?

[bgsengine]

do a compression check and see if it has too much compression - might be the decompression system is bad

Adding: kickback or backfire while cranking is what I am thinking - or hydrolocked cylinder if it happened to load up with gas.

[Fulltilt]

Along those lines, you may want to check the flywheel/crank key. It will sometimes shear/partly shear after an impact,or backfire, and cause all kinds of grief.
Service manual can be downloaded here : https://power.kohler.com/na-en/engines/manuals

Though, as long as I've been working on small engines, I've never ran across a bent starter shaft, and I've seen lots of sheared keys.

[lee]

I straightened the shaft the best I could, put the starter back together and tested it. Works fine and the shaft has just a little wobble. Installed on engine and it spins it over just fine and sounds normal. Cold compression is 85 psi. That doesn't sound like too much does it? I think Briggs are around 60-70 psi right. This is engine is on a Craftsman lawn tractor so I'm thinking there is no way the engine would stop fast enough to shear the key. I'm going to check it anyway. The keyways on the flywheel and crankshaft should be lined up straight across right?

[RoyM]

That starter likely won't last long, the obviously weak shaft has been further compromised by bending and straightening. The oem starter is definitely not cheap but may be the only way to go.

[Fulltilt]

This is engine is on a Craftsman lawn tractor so I'm thinking there is no way the engine would stop fast enough to shear the key. I'm going to check it anyway. The keyways on the flywheel and crankshaft should be lined up straight across right?

Well, I've seen more than a couple sheared keys on lawn tractors...trust me.

Yeah, the keyways need to be perfectly aligned, but I would pull the flywheel.

[Arkie]

Doubtful that the starter will remain good for very long and may damage your flywheel starter ring is it happens again.
The Bendix gear probably failed to immediately retract right when the engine started and when the Bendix teeth boundup on the flywheel it bent a aftermarket starter shaft. That shaft is now weaker and being aftermarket it was probably made in CHINA. (out of aluminum beer cans)Donald Trump is going to stop the import of this China made stuff.
I would replace the complete starter and Bendix drive and look at the flywheel teeth (inspect every tooth) very carefully.

[lee]

Update: The starter with the straightened shaft is still working and sounds ok after 50+ starts. I have noticed that during normal use this engine will backfire during starting every now and then. The engine always starts and runs great even if it backfires while starting like it did today. I checked the flywheel key a while back and it was ok. What else would cause this engine to randomly backfire while starting? Could the timing advance module that is on this engine have something to do with it? I'm thinking a random backfire bent the starter shaft, so I would like to correct this if possible before I throw an expensive new oem starter on it. With my luck I'd be sitting here with 2 bent starter shafts and still not be sure what caused the problem. I'd be willing to bet the reason why there's a relatively new looking aftermarket starter on this engine now is the previous owner had this same problem and it bent the oem starter shaft that came on this engine.

[KE4AVB]

Just to clarify...Is this so called backfire from the exhaust or the intake? I know refer both as backfire when the one from the exhaust is technically an after-fire.

And yes the ignition system failures can cause either one. I had both over the years. One was Kawasaki that go off like 12Ga shotgun ramdonly. Nearly set my pants leg on fire one time with it shooting out a 12" flame and the sound didn't help my nerves much either when it first did it. That one turn out to a failing ignitor (electronic coil trigger). Then there was the Homelite chainsaw that literally set the air filter on fire randomly; also was a failing coil pack electronics. And this is very dangerous especially since the saw was a 2 cycle and this ignition had go though the crankcase.

These two cases were the worse I have seen in my shop but I had milder cases too.

[Arkie]

Look at the flywheel rotation (watch carefully) as the engine is cranking and note if the flywheel rotation stays same when it backfires. If it's backfiring out the exhaust, If it kicks back or the flywheel rotation slows down the timing is too fast, but usually BTDC timing will cause kickback and backfire out intake valve. If it does not slow down or kick back when backfires out the exhaust the timing is little slow or the comp release or exhaust valve is slightly open when she fires and this should not cause a starter Bendix issue. (intermittent reverse kickback would be a concern.

I would look very close at each tooth on with the flywheel removed and turned upside down for good easy viewing. (and also closely examine the Bendix gear teeth.
Sometimes just one or two teeth next too each other will get a small double notch notch on the underside and cause Bendix engaugement mesh issues intermittently. Also make sure that the groove BETWEEN each FLYWHEEL tooth is same depth. (one or two does not have a piece of casting or foreign material between the teeth.

Is the Bendix gear metal or hard fiber?
Is it backfiring out the exhaust or back thru the carb?
I would not be too concerned about a exhaust backfire causing starter SHAFT damage.